To establish a correlation between dislocations and deep levels in GaN, a deep-level transient spectroscopy study was carried out on GaN samples grown by metalorganic chemical vapour deposition. In addition to typical undoped and Si-doped GaN samples, high-quality crack-free undoped GaN film grown intentionally on heavily doped cracked Si-doped GaN and cracked AlGaN templates were also chosen for this study. The purpose of growth of such continuous GaN layers on top of the cracked templates was to reduce the screw dislocation density by an order of magnitude. Deep levels in these layers were characterized and compared with emphasis on their thermal stabilities and capture kinetics. Three electron traps at Ec–ET~0.10–0.11, 0.24–0.27 and 0.59–0.63eV were detected common to all the samples while additional levels at Ec–ET~0.18 and 0.37–0.40eV were also observed in the Si-doped GaN. The trap levels exhibit considerably different stabilities under rapid thermal annealing. Based on the observations, the trap levels at Ec–ET~0.18 and 0.24–0.27eV could be associated with screw dislocations, whereas the level at Ec–ET~0.59–0.63eV could be associated with edge dislocations. This was also in agreement with the transmission electron microscopy measurements conducted on the GaN samples.

Identification of Deep Levels in GaN Associated with Dislocations. C.B.Soh, S.J.Chua, H.F.Lim, D.Z.Chi, W.Liu, S.Tripathy: Journal of Physics - Condensed Matter, 2004, 16[34], 6305-15